Joint



' F. H. BANCROFTQ- JJJJ T.

' APPLICATION MAY 24, 1919. 1,391,163, PatentedSept. 20, 1921.

d I I77 ve 7720 7 2 21271271307? era/f 27y w azwq awm his 3W0 r7769 UNITED STATES PATENT OFFICE. 1

FRANK IE. BANCROFT, OF GARDNER, MASSACHUSETTS; ASSIGNOR TO I. DERBY &:

GOMPANY, OF GARDNER, MASSACHUSETTS, A CORPORATION OF MASSACHU- sm'rs. v r

and rounds, or a seat, supporting legs, rounds,

back pillars or other wooden members, and for the purpose of illustration the invention is herein shown and described in connection with such articles of furniture. It is,- .however, to bedistinctly understood that the description of my improved j oint as applied to an article of furniture is illustrative only and that its utility is by no means limited to the specific example shown.

In the manufacture of wooden articles such as chairs it has heretofore been difiicult to secure the various members together in such manner as to withstand the rack and strain to which such articles are customarily subjected. The strength of the usual glued socket joint by means of which the back pillars, legs and rounds of a chair are joined to the seat and to each other,. depends upon the tightness of the joint between the socket member and the member fitting therein and the adhesion of the glue employed. Under customary conditions of use, the wood in the chair quickly dries out in the dry atmosphere of the room causing a shrinkage of the wood and a consequent loosening of the joint. As soon as the chair is subjected to a severe strain the members separate at the joint and unless repaired the chair quickly goes to pieces The principal object of the invention is to provide an improved socket joint for securing the wooden members of furniture and similar articles together which will hold under severe usage, and which is easily and economically made, entailing no additional labor in the manufacture of the article.

In order to more clearly set forth the na ture of my invention I have illustrated one Specification of Letters Patent. Patented Sept. 20, 1921.

Application filed May 2 4, 1919. Serial No. 299,500. 1

embodiment thereof in the accompanying drawing in wh1ch,-

Figure 1 is a side elevation partly in sec- 7 tion of a stool showing the seat and around secured to the leg by means of the improved joint of this invention; r

, Fig. 2 is a detailsectional view through a joint between a chair leg and a round;

. Fig. 3 is a section taken on line 33 of Fig. 2 and Fig. 4 is a section of a modified form of joint.

The stool illustrated inFig. 1 comprises a seat 1 supported by legs 2 which are connected by rounds 8. The underside of the seat is provided with sockets 4 into which the upper ends of the legs 2 are driven. The base of each socket is provided with a tubular wedge-shaped ridge of wood 5 integral with the seat, which may be conveniently formed by boring the socket 4 with a boring tool so constructed as to bore the socket leaving the tubular ridge of wood. 1 5

The upper end of the leg 2 which is adapted to fit into the socket tis provided with an annular kerf 6 ofrless width than the base of ridge 5, but of substantially the same depth as said ridge. This kerf may be made on'a lathe during the process of turning the leg, may be sawed in by an annular kerfing saw, or formed in any other suitable manner.

The round 3 is joined to the leg 2 in a similar manner, the leg being provided with a socket 7 having a wedge-shaped ridge of wood 8 formed integrally on thebase of the socket, which cooperates with an annular kerf 9 cut in the end of round 3. I

In securing the leg 2 to the seat 1, the leg is inserted into the socket opening and driven inwardly until the end of the le becomes seated on the base of the socket. s the leg enters the socket, the point of wedge 5 enters the kerf 6 so that further inward driving of the leg forces the annular wedge into kerf 6 spreading or expanding the top of the leg to fill the socket.

The rounds 3 are wedged into sockets in the legs 2 in a manner similar to that in which the legsare secured to the seat. The socket 7 is bored into the side of the leg across the grain of the wood, and thus the grain runs transversely through the tubular ridge 8, while the kerf 9 is out with the grain into the end of round 3. Referring to Fig. 3,

wherein the grain of the wood in the leg 2.

is indicated by .the longitudinal shade lines, it will be evident that the tubular wedge 8 will be far more compressible at point 10.

where the compressive force is applied against the side of the fibers of the wood, than at point 11 where the compressiveforce is applied against the ends of the fibers. The result is that the greatest wedging action 7 takes place at point 11 and the strain is transmitted longitudinally of the leg and the least wedging action takes place at point vl0 where any great strain would tend to split the leg.

' The socket may be tapered as shown at 12 in Fig. 4, by cutting the socket with an ins creasingly larger diameter toward its base. The base of the socket is provided with a tubular wedge 13, whose inner wall 14 is perpendicular to the base of the socket .and whose outer wall 15 has a taper greater than the taper of the wall of the socket. WVhen the leg 2 is driven into socket 12 the wedge 13 expands the end of leg 2 until the tapered socket is filled. An exceedingly strong joint is thus secured.

By the construction above described the socketed joints between wooden members may be readily and economically made, and through the inherent character of the tubular wooden wedge,'a wedged joint secured without danger of splitting either of the joined members.

I claim: p

1.- A joint for wooden articles comprising a wooden memberhaving a socket, a tubular ridge of wood projecting integrally from the base of said socket, and a second wooden projecting from thebase of the socket, and a. second member havlng a kerf formed in the end thereof and running with the grainof the wood, said second member bein adapted to fit into said socket, the said rldge co- 7 operating with said kerf to expand the end of said second member in said socket.

3. A joint for wooden articles comprising a member having a socket cuttherein across the grain of the woodin such a manner'as to leave a tubular ridge projecting-from the base of the socket, and a'second member hav- I ing a kerf formed in the end thereof and running with the grain of the wood, -said second member being adapted to fit-i'nto "said socket, the said 'ridgecooperating with said kerf to expand the end of said fsecond' member in said-socket.-

4. The method of joining wooden members which consists in formingan undercut socket in one of the m'embers'in such manner as to leave an integral tubular wedge protruding from the bottom thereof, cut ting an annular kerf in the end of the other member into -which the wedge ofithe first member may enter, and forcingthe' mem bers together so th'at'the'we'dge of the first member enters the kerf oithe secondmember expandln'g theend of the secondmember in the socket of the first member.

Signed by me at Boston, Mass.,thi-si20th day of May, 1919.

' FRANK H. BANCROFT. 

